consider failing earlier when no device is provided

[tabowling]

I accidentally executed a playbook using the storage role where I did not have a device defined. Would it be good to detect very early that a device name is NULL or invalid before executing so much of the logic? Below is the snippet from my playbook:

    - name: Configure Image Builder Storage
      include_role:
        name: linux-system-roles.storage
      vars:
        use_partitions: false
        storage_pools:
          - name: image_builder
            disks: ['']  # something like vdb
            # type: lvm
            state: present
            volumes:
              - name: composer
                size: "19.5G"
                # type: lvm
                # fs_type: xfs
                fs_label: "imgbldr"
                mount_point: '/var/lib/lorax/composer'
      when: CONFIG_STORAGE

[tabowling]

here is the output it generated:

`
TASK [linux-system-roles.storage : define an empty list of pools to be used in testing] ***************************************
ok: [rhel8beta]

TASK [linux-system-roles.storage : define an empty list of volumes to be used in testing] *************************************
ok: [rhel8beta]

TASK [linux-system-roles.storage : include the appropriate backend tasks] *****************************************************
included: /usr/share/ansible/roles/linux-system-roles.storage/tasks/main-blivet.yml for rhel8beta

TASK [linux-system-roles.storage : get a list of rpm packages installed on host machine] **************************************
skipping: [rhel8beta]

TASK [linux-system-roles.storage : make sure blivet is available] *************************************************************
changed: [rhel8beta]

TASK [linux-system-roles.storage : initialize internal facts] *****************************************************************
ok: [rhel8beta]

TASK [linux-system-roles.storage : Apply defaults to pools and volumes [1/6]] *************************************************
ok: [rhel8beta] => (item={'name': 'image_builder', 'disks': [''], 'state': 'present', 'volumes': [{'name': 'composer', 'size': '19.5G', 'fs_label': 'imgbldr', 'mount_point': '/var/lib/lorax/composer'}]})

TASK [linux-system-roles.storage : Apply defaults to pools and volumes [2/6]] *************************************************
ok: [rhel8beta] => (item=[{'state': 'present', 'type': 'lvm', 'name': 'image_builder', 'disks': [''], 'volumes': [{'name': 'composer', 'size': '19.5G', 'fs_label': 'imgbldr', 'mount_point': '/var/lib/lorax/composer'}]}, {'name': 'composer', 'size': '19.5G', 'fs_label': 'imgbldr', 'mount_point': '/var/lib/lorax/composer'}])

TASK [linux-system-roles.storage : Apply defaults to pools and volumes [3/6]] *************************************************
ok: [rhel8beta] => (item=[{'name': 'composer', 'size': '19.5G', 'fs_label': 'imgbldr', 'mount_point': '/var/lib/lorax/composer'}, {'state': 'present', 'type': 'lvm', 'size': 0, 'fs_type': 'xfs', 'fs_label': '', 'fs_create_options': '', 'fs_overwrite_existing': True, 'mount_point': '', 'mount_options': 'defaults', 'mount_check': 0, 'mount_passno': 0, 'mount_device_identifier': 'uuid'}])

TASK [linux-system-roles.storage : Apply defaults to pools and volumes [4/6]] *************************************************
ok: [rhel8beta] => (item={'state': 'present', 'type': 'lvm', 'name': 'image_builder', 'disks': [''], 'volumes': [{'name': 'composer', 'size': '19.5G', 'fs_label': 'imgbldr', 'mount_point': '/var/lib/lorax/composer'}]})

TASK [linux-system-roles.storage : Apply defaults to pools and volumes [5/6]] *************************************************
ok: [rhel8beta] => (item={'state': 'present', 'type': 'lvm', 'name': 'image_builder', 'disks': [''], 'volumes': [{'name': 'composer', 'size': '19.5G', 'fs_label': 'imgbldr', 'mount_point': '/var/lib/lorax/composer'}]})

TASK [linux-system-roles.storage : Apply defaults to pools and volumes [6/6]] *************************************************

TASK [linux-system-roles.storage : debug] *************************************************************************************
ok: [rhel8beta] => {
"_storage_pools": [
{
"disks": [
""
],
"name": "image_builder",
"state": "present",
"type": "lvm",
"volumes": [
{
"fs_create_options": "",
"fs_label": "imgbldr",
"fs_overwrite_existing": true,
"fs_type": "xfs",
"mount_check": 0,
"mount_device_identifier": "uuid",
"mount_options": "defaults",
"mount_passno": 0,
"mount_point": "/var/lib/lorax/composer",
"name": "composer",
"pool": "image_builder",
"size": "19.5G",
"state": "present",
"type": "lvm"
}
]
}
]
}

TASK [linux-system-roles.storage : debug] *************************************************************************************
ok: [rhel8beta] => {
"_storage_volumes": []
}

TASK [linux-system-roles.storage : manage the pools and volumes to match the specified state] *********************************
fatal: [rhel8beta]: FAILED! => {"actions": [], "changed": false, "leaves": [], "mounts": [], "msg": "unable to resolve any disks specified for pool 'image_builder' ([''])", "pools": [], "volumes": []}

PLAY RECAP ********************************************************************************************************************
rhel8beta : ok=24 changed=1 unreachable=0 failed=1 skipped=6 rescued=0 ignored=0

`